Baingio Pinna, and Stephen Grossberg (2005).
The watercolor illusion and neon color spreading: A unified analysis
of new cases and neural mechanisms. Journal of the Optical Society of
America A, in press.

ABSTRACT
Coloration and figural properties of neon color spreading and the
watercolor illusion are studied using phenomenal and psychophysical
observations. Coloration properties of both effects can be reduced to
a common limiting condition, a nearby color transition called the
"two-dot limiting case", that clarifies their perceptual similarities
and dissimilarities. The results are explained by the FACADE neural
model of biological vision. The model proposes how local properties
of color transitions activate spatial competition among nearby
perceptual boundaries, with boundaries of lower contrast edges
weakened by competition more than boundaries of higher contrast
edges. This asymmetry induces spreading of more color across these
boundaries than conversely. The model also predicts how depth and
figure-ground effects are generated in these illusions.